target/riscv: add shcounterenw

target/riscv: add shcounterenw

shcounterenw is defined in RVA22 as:

"For any hpmcounter that is not read-only zero, the corresponding bit in
hcounteren must be writable."

This is always true in TCG so let's claim support for it.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241218114026.1652352-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>